Process for pure carbon production

ABSTRACT

The disclosure provides for methods of oxidizing carbide anions, or negative ions, from salt like carbides at low temperatures below about 600° C. In another aspect, the disclosure provides for reactions with intermediate transition metal carbides. In yet another aspect, the disclosure provides for a system of reactions where salt-like carbide anions and intermediate carbide anions are oxidized to produce pure carbon of various allotropes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.61/798,198, filed Mar. 15, 2013, which is incorporated herein byreference in its entirety.

FIELD

The disclosure provides for methods of oxidizing carbide anions, ornegative ions, from salt like carbides at low temperatures below about600° C. In another aspect, the disclosure provides for reactions withintermediate transition metal carbides. In yet another aspect, thedisclosure provides for a system of reactions where salt-like carbideanions and intermediate carbide anions are oxidized to produce purecarbon of various allotropes.

BACKGROUND

Carbides are chemical compounds containing carbon and an element withlower electronegativity, or less of an ability to attract electrons.Nearly all elements react with elemental carbon to produce carbides.They are further classified into four groups: salt-like carbides,covalent carbides, interstitial carbides, and intermediate transitionmetal carbides. Salt-like carbides react with water and dilute acids toproduce metallic cations and hydrocarbon gases. Intermediate transitionmetal carbides also react with dilute acid and sometimes water toproduce hydrocarbons, metallic cations and sometimes hydrogen.

The salt-like carbides are further broken down into methanides,acetylides, and sesquicarbides. Methanides react with water to producemethane. Methane includes a carbon atom bonded to four hydrogen atoms inan sp3 hybridization. Two examples of these methanides are aluminumcarbide (Al₄C₃) and beryllium carbide (Be₂C). Acetylides are salts ofthe acetylide anion C₂ ²⁻ and also have a triple bond between the twocarbon atoms. Triple bonded carbon has an sp 1 hybridization and twoexamples of acetylides are sodium carbide (Na₂C₂) and calcium carbide(CaC₂). Sesquicarbides contain the polyatomic ion C₃ ⁴⁻ and containscarbon atoms with an sp1 hybridization. Two examples of sesquicarbidesare magnesium (Mg₂C₃) and lithium (Li₄C₃).

In 1919, patents were filed that defined an oxidization reaction toproduce potassium metal by reacting potassium cations (positive ions)with acetylide anions from calcium carbide. The reacting medium wasmolten potassium fluoride. This is shown in the reaction in Equation (1)below:

Equation 1

2KF+CaC₂→CaF₂+2K° +2C°_((graphite)) reaction T=800° C.   (1)

The other products of that reaction are calcium fluoride and graphite.Graphite is the most thermodynamically stable form of elemental carbon,and this is therefore the favored product at high temperature. Thisreaction, the reduction of the potassium ion, takes place at about 800°C. which would be considered high temperature since 600° C. is red heat.

SUMMARY

The disclosure provides for a method of oxidizing carbide anions and/ornegative ions from carbides by oxidizing carbide anions at a reactiontemperature of below 600° C., wherein the reaction produces an allotropeof carbon in an sp1 and/or sp3 configuration.

In another aspect, the disclosure provides for a method of producingpure elemental allotropes of carbon by oxidizing salt-like carbideanions and/or intermediate carbide anions at a reaction temperature ofbelow 600° C.

In yet another aspect, the disclosure provides for a method of producingdiamonds by reacting carbides with molten metallic halide salts attemperatures below 600° C.

The disclosure also provides for a method of controlling a carbonallotrope by controlling the reduction potential of a low melting pointhalide salt reactant by varying the reduction potential of cationsand/or changing the temperature of the melt.

In an aspect, the carbide anions are salt-like or intermediate carbideanions. In another aspect, the salt-like carbide anions are selectedfrom the group consisting of methanides, acetylides, and sesquicarbides.In another aspect, the salt-like carbide anion is calcium carbide.

In an aspect, the methods described herein produce an allotrope ofcarbon in an sp1 configuration. In yet another aspect, the methodsdescribed herein produce an allotrope of carbon in an sp3 configuration.

The method disclosure also provides for methods described herein whereinthe reaction temperature is below 300° C. and methods described hereinfurther including adding a salt with a melting point of less than 250°C. as a reactant.

DETAILED DESCRIPTION

In an aspect, the disclosure provides for methods of oxidizing carbideanions, or negative ions, from salt like carbides at low temperaturesbelow about 600° C. Oxidization means that the ion being oxidized givesup electrons. The negative ions of the salt like carbides are reacted toproduce elemental carbon in its various allotropes, or crystalstructures, with sp1, sp2, and/or sp3 hybridizations. In another aspect,the disclosure provides for reactions with intermediate transition metalcarbides. In yet another aspect, the disclosure provides for a system ofreactions where salt-like carbide anions and intermediate carbide anionsare oxidized to produce pure carbon of various allotropes.

The methodology described herein can be distinguished from previousreactions patented in 1919 for several reasons. For one, the reaction inequation (1) occurs at high temperatures of around 800° C. in previouslyknown reaction mechanisms whereas the methodology described hereinincludes reactions at lower temperatures below around 600° C. Second,the reaction in equation (1) only produces graphite as a pure carbonproduct. Graphite is a crystalline allotrope of carbon with an sp2hybridization. Until now, it was not recognized that such a reactionprovides for a diamond with an sp3 hybridization, superconductingmaterial with an sp1 hybridization, fullerenes, carbon nano tubes, orany of other forms of pure carbon. To this end, the disclosuredifferentiates from what was previously recognized in the art.

In an aspect, the first step of the reaction system is to oxidize thecarbide ions at low temperature below 600° C., but typically thereactions occur below 300° C. The reactions use low melting point salts,for example stannous chloride (SnCl₂), that have melting points lessthan 280° C. as the reactants. The reaction medium is the molten salt,for example, molten stannous chloride. This means that there is anexcess of salt during the reaction which takes place in the molten saltliquid. Chemically, the cation (positive ion) of the salt is reduced tothe elemental state. Therefore, stannous ion Sn⁺² would become elementaltin)(Sn°). The standard reduction potential of the stannous ion Sn⁺² isonly about −0.136V. Reduction potential refers to the ability of achemical species to acquire electrons and thus have its charge reduced.So not much energy is required to reduce the stannous ion, therefore thereaction reacts to completion. There is an excess of reduction potentialin the carbide anions since they are shown to reduce the potassium ionin Equation (1) which requires −2.94V.

The reduction of Sn⁺² by acetylide or any carbide anion is not mentionedanywhere in the literature. Only certain metallic salts are applicablefor this reaction. It is preferred that the cation of the salt does notproduce a carbide by direct reaction with carbon at low temperatures orthe temperature of the reduction reaction. If the cation does producecarbide, then pure carbon would not be produced. Examples of thepreferred salts contain tin, lead, mercury, and zinc. Furthermore, thesalts must have a low melting point. The temperature of the reactionmust be high enough to melt the salts but low enough to control theelectronic hybridization of the carbon. As mentioned in the backgroundinformation, graphite is the most thermodynamically stable form of purecarbon. So if the temperature of the reaction is too high, the purecarbon will form crystalline graphite in the sp2 hybridization insteadof the desired sp1 or sp3 hybridizations.

The next item in the reaction system is the low temperature oxidation ofmethanides to produce diamond, or carbon in that has an sp3hybridization. Aluminum carbide (Al₄C₃) and beryllium carbide (Be₂C) arethe only two known salt like carbides that produce methane when theyreact with water. The methane molecule contains a carbon atom in the sp3hybridized state, which is the same as diamond. The idea is to oxidizethe methanide anion in a controlled manner at temperatures low enough tomaintain the electronic configuration, or sp3 hybridization and producediamond. Thus, the controlled oxidization of aluminum carbide at lowenough temperatures will preferentially produce diamonds. This reductiontakes place at about 280° C. and atmospheric pressure.

Oxidation of the methanide (aluminum carbide) anion in molten tin halidesalt blends to produce diamond. There is no literature that mentions thereduction of aluminum carbide much less anything that mentions thisreaction to produce diamond, or sp3 hybridized carbon. Experiments forthis reaction have been carried out using stannous fluoride (SnF₂) andstannous chloride (SnCl₂), which have melting points of 214° C. and 235°C., respectively. These reactions can be seen in Equation (2) andEquation (3) below:

Equation 2

Al₄C₃+6SnF₂→6Sn°+4AlF₃+3C°_((diamond) 1reaction at T=)235° C.   (2)

Equation 3

Al₄C₃+6SnCl₂→6Sn°+4AlCl₃+3C°_((diamond)) reaction at T=280° C.   (3)

The proof of the diamond, or carbon with sp3 hybridization, materialproduced was established using X-Ray Diffraction patterns (XRD) both atWVU and independently at Wright Patterson Air Force Base. Early diamondproduction studied certain metallic catalysts needed to make diamonds.These catalysts gave similar XRD patterns to diamonds which caused someconfusion. However, no metallic catalysts or catalysts of any kind wereused in this system of reactions. The fact that diamonds were producedwas unexpected and provides support for the experiments describedherein.

Since the chemical hypothesis to maintain the sp3 hybridization of purecarbon is confirmed with the production of diamonds, it can extended toinclude the potential superconducting material to maintain the sp1hybridization of pure carbon. From the literature, there have been manydifferent attempts to make this material but none have been successful.The process begins with a carbide that contains carbon in an sp1hybridized state. As mentioned in the background information, acetylideshave the ability to satisfy this requirement. The most common example iscalcium carbide (CaC₂). However, sp1 carbon in the acetylide anion canbe reconfigured even at very low energy or low temperatures. A moredesired reactant is one that has a tendency to maintain the sp1configuration throughout the rigors of the reaction. The disclosureprovides for two compounds that have the ability to act as a sufficientreactant: magnesium sesquicarbide (Mg₂C₃) and lithium sesquicarbide(Li₄C₃), also mentioned in the background information. From theliterature, a structural analysis using X-Ray diffraction was completedand shows that two of the carbon atoms are equivalent with an sp1configuration. With a hydrolysis reaction, methyl acetylene (CH₃C₂H) isproduced. One terminal carbon, the methyl carbon (CH₃) end is sp3 innature while the other two carbons maintain their sp1 character. Thegoal is to polymerize the carbon atoms while maintaining the sp1configuration. This would produce a completely new allotrope of carbonthat has an sp1 configuration. Due to the electronic properties of sucha material, it may be a high temperature superconductor. Based on theliterature, this approach has never been attempted.

EXAMPLES Example 1

In an oxygen moisture free environment, aluminum carbide, Al₄C₃ wasground to less than 20 mesh. A quantity of anhydrous stannous chloride,SnCl₂ was blended with the ground aluminum carbide at twice thestoichiometric ratio for the reaction below

Al₄C₃+6SnCl₂→4AlCl₃+6Sn+3C

The blend was poured into a glass ampoule that was subsequently placedinto a stainless steel tube. The stainless steel tube was sealed andremoved from the controlled environment. The tube and its contents wereheated to 280° C. for 2 hours. The contents of the ampoule were washedwith 6M HCl to remove all the aluminum chloride, excess stannouschloride and Sn metal. The remaining carbon was in two forms (1) agraphene like compressed set of platelets and (2) a cubic/orthorhombicdiamond like structure. The preponderance of the carbon product was thelatter structure.

Example 2

In an oxygen moisture free environment, calcium carbide, CaC₂ was groundto less than 20 mesh. A quantity of anhydrous zinc chloride, ZnCl₂ wasblended with the ground aluminum carbide at twice the stoichiometricratio for the reaction below

3CaC₂+3ZnCl₂→3CaCl₂+3Zn+6C

The blend was poured into a glass ampoule that was subsequently placedin a stainless steel tube. The stainless steel tube was sealed andremoved from the controlled environment. The tube and its contents wereheated to 425° C. for 2 hours. The contents of the ampoule were washedwith 6M HCl to remove all the Zinc chloride, calcium chloride, and Znmetal. The remaining carbon was in two forms (1) a graphene likecompressed set of platelets and (2) a cubic/orthorhombic diamond likestructure. The preponderance of the carbon product was the latterstructure.

Example 3

In an oxygen moisture free environment, calcium carbide, CaC₂ was groundto less than 20 mesh. A quantity of anhydrous stannous chloride, SnCl₂was blended with the ground aluminum carbide at twice the stoichiometricratio for the reaction below

3CaC₂+3SnCl₂→3CaCl₂+3Sn+6C

The blend was poured into a glass ampoule that was subsequently placedin a stainless steel tube. The stainless steel tube was sealed andremoved from the controlled environment. The tube and its contents wereheated to 280° C. for 2 hours. The contents of the ampoule were washedwith 6M HCl to remove all the stannous chloride, calcium chloride, andSn metal. The remaining carbon was in only one form a graphene likecompressed set of platelets

What is claimed is:
 1. A method of oxidizing carbide anions and/ornegative ions from carbides, said method comprising: oxidizing carbideanions at a reaction temperature of below 600° C., wherein the reactionproduces an allotrope of carbon in an sp1 and/or sp3 configuration. 2.The method of claim 1, wherein said carbide anions are salt-like orintermediate carbide anions.
 3. The method of claim 2, wherein saidsalt-like carbide anions are selected from the group consisting ofmethanides, acetylides, and sesquicarbides.
 4. The method of claim 2,wherein said salt-like carbide anions are acetylides.
 5. The method ofclaim 1, wherein said reaction produces an allotrope of carbon in an sp1configuration.
 6. The method of claim 1, wherein said reaction producesan allotrope of carbon in an sp3 configuration.
 7. The method of claim1, wherein said reaction temperature is below 300° C.
 8. The method ofclaim 3, wherein said carbide anion is calcium carbide.
 9. The method ofclaim 1, wherein said reaction further comprises adding a salt with amelting point of less than 250° C. as a reactant.
 10. A method ofproducing pure elemental allotropes of carbon comprising: oxidizingsalt-like carbide anions and/or intermediate carbide anions at areaction temperature of below 600° C.
 11. The method of claim 10,wherein said salt-like carbide anions are selected from the groupconsisting of methanides, acetylides, and sesquicarbides.
 12. The methodof claim 10, wherein the reaction produces pure elemental allotropes ofcarbon with a sp1 or sp3 configuration.
 13. The method of claim 12,wherein said reaction produces pure elemental allotropes of carbon witha sp1 configuration.
 14. The method of claim 12, wherein said reactionproduces pure elemental allotropes of carbon with a sp3 configuration.15. The method of claim 10, wherein said reaction temperature is below300° C.
 16. The method of claim 10, wherein the reaction furthercomprises utilizing a salt with a melting point of less than 250° C. asa reactant.
 17. The method of claim 10, wherein said reaction comprisesreacting a sesquicarbide with a molten metallic halide salt to produce apure allotrope of carbon in the sp1 configuration.
 18. A method forproducing diamonds by reacting carbides with molten metallic halidesalts at temperatures below 600° C.
 19. The method of claim 18, whereinsaid reaction temperature is below 300° C.
 20. A method of controlling acarbon allotrope comprising: controlling the reduction potential of alow melting point halide salt reactant by varying the reductionpotential of a cation and/or changing the temperature of the melt.